Nintendo shares have soared almost 90% since "Pokémon Go" was launched just eight days ago.

The gaming company, now valued at $3.94 billion (£2.94 billion), has become one of Japan's 20 largest businesses, The Financial Times reports. It now has a bigger market cap than the likes of automotive beast Mitsubishi and brokerage giant Nomura.

Shares in the Kyoto-headquartered company surged more than 9% on the Toyko stock market on Friday even though it owns just 33% of the Pokémon Company and an estimated 5-10% stake in the game's developer, Niantic.

This crazy hype may well drop off over time. While the game is hugely popular, it's not clear whether Niantic can build it into a sustainable business — or if it will just be a passing fad.

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But the game hasn't been without its issues. Overwhelming demand has put pressure on Pokémon Go's servers meaning many players have struggled to catch pokémon due to unexpected software crashes.

There have also been a number of physical incidents that have occurred due the game's augmented reality feature. Two men fell off a cliff in San Diego, California, while on the hunt for Pokémon while others are being warned not to play the game while driving.